Hypercapnia (HC) challenge provides an excellent model
condition for studying brain activity. We investigated the effect of HC on
Resting State Network (RSN) and compared it with that on visual-evoked BOLD
signals. We found that RSN shows a reduction in both cluster size and signal
amplitude due to HC challenge. We also found a similar reduction of visual fMRI
signal in the same subjects. This result indicates that vascular effects such
as basal CBF and venous oxygenation contribute to the reduction of RSN as they
do to visual fMRI signal. Thus, caution should be used in interpreting BOLD RSN
changes.